Ascaridoid nematode infection in haddock ( Melanogrammus aeglefinus ) and whiting ( Merlangius merlangus ) in Northeast Atlantic waters

Abstract

Haddock and whiting are two species of the family Gadidae that are exploited by fisheries mainly in European waters, the former being one of the most important seafood resources in Scotland (UK). The present study aimed to quantify prevalence, abundance and intensity of infection of the zoonotic parasite Anisakis spp. and other ascaridoid nematodes in these fish as part of a study on the risk to consumers. Fish were sourced from research trawling surveys during 2013-2015, aiming to cover a range of size-classes and different times of year. Samples were obtained from the North Sea, west coast of Scotland and the Barents Sea. Fish were stored frozen prior to separation of viscera and fillets and the use of pressing and UV visualisation to locate, identify and count Anisakis spp. and other ascaridoids in fillets (divided into 8 parts), liver and other viscera. A subsample of Anisakis spp. collected from haddock were identified genetically by means of two diagnostic markers (mtDNA cox2 and EF1 α-1 nuclear DNA), and all were identified as A. simplex (s. s.). Both fish species showed moderate to high infection levels with Anisakis spp. (likely A. simplex (s. s.)) in the visceral organs and cavity, and rather low infection in the musculature. Those A. simplex (s. s.) larvae present in the musculature were mostly found in the anterior ventral area. In both fish species, the infection rate increased with fish length and in haddock a negative relationship was observed between Anisakis spp. numbers in muscle and body condition. From our sampling of Anisakis spp. in fish muscle, in Scotland, whiting presents a greater human health risk than haddock in Scotland. The risk arising from consumption of haddock from the Barents Sea (with 72% prevalence of Anisakis) is markedly higher, although in all cases the risk of infection in humans can be minimised if fish are frozen or adequately cooked prior to consumption. We present previously unpublished information on reported cases of anisakiasis in the United Kingdom during 2000-2013, which included 4 cases from Scotland among 22 overall. While these findings suggest that anisakiasis is relatively rare in the UK, underreporting is likely and further investigation of the incidence of anisakiasis is needed.

It’s a wormy world: Meta‐analysis reveals several decades of change in the global abundance of the parasitic nematodes Anisakis spp. and Pseudoterranova spp. in marine fishes and invertebrates

“…abundance across the time frame of our study appears to be robust across host species, but the positive temporal trend we reveal here was strongly driven by the northeastern Atlantic. Mattiucci et al, 2014Mattiucci et al, , 2018Pierce et al, 2018). Some of these cetacean species have increased in abundance since International Whaling Commission regulations came into effect in the mid-1980s…”

“…It is also possible that recent increases in cetacean populations have been especially influential in the northeastern Atlantic. This region is dominated by Anisakis simplex sensu stricto, whose definitive hosts include minke whales ( Balaenoptera acutorostrata ), common dolphins ( Delphinus delphis ), long‐finned pilot whales ( Globicephala melas ), white‐beaked dolphins ( Lagenorhynchus albirostris ), killer whales ( Orcinus orca ), and striped dolphins ( Stenella coeruleoalba ; Bilska‐Zajac et al, 2015; Mattiucci et al, 2014, 2018; Pierce et al, 2018). Some of these cetacean species have increased in abundance since International Whaling Commission regulations came into effect in the mid‐1980s (e.g., Hammond et al, 2013; Murphy, Pinn, & Jepson, 2013; Skaug, Oien, & Bothun, 2004).…”

Increasing intensities of Anisakis simplex third-stage larvae (L3) in Atlantic salmon of coastal waters of Scotland

“…These support the observations of similar studies, which have recorded higher Anisakis sp. prevalence and intensity in haddock (Melanogrammus aeglefinus (L.)) [65], and Atlantic cod [66] in populations sampled from the Barents Sea. With the relative abundance of both large whales and dolphins highest in the Faroe-Shetland Channel [67], and a diverse cetacean population in the Barents Sea [68], these results further demonstrate the potential significance of regional definitive host abundance in prevailing A. simplex (s.l.)…”

Anisakid parasites (Nematoda: Anisakidae) in 3 commercially important gadid fish species from the southern Barents Sea, with emphasis on key infection drivers and spatial distribution within the hosts

“…[molecularly identified as P. decipiens (s.s.) and P. krabbei] apparently showed no side preference but seemed to occur more frequently in the belly flaps. In Barents Sea haddock examined by Pierce et al (2018), A. simplex (s.s.)…”